JP2002244318A - Method for producing pigment dispersion for producing electrophotographic photoreceptor and electrophotographic photoreceptor using this dispersion - Google Patents

Abstract

(57) [Summary] [Problem] To prepare a pigment dispersion for producing an electrophotographic photoreceptor having good dispersibility and stability over time and excellent coating properties, and using this dispersion, high sensitivity and repetition characteristics are obtained. To provide an excellent electrophotographic photoreceptor. In a method for producing a pigment dispersion for producing an electrophotographic photoreceptor, which comprises dispersing a pigment for a charge generating substance in an organic solvent in which at least one or more binders are dissolved, the pigment dispersion has a concentration lower than the final concentration. At a high solids concentration, the total amount of the pigment for the charge generating substance to be dispersed is 1% of the total binder amount.
A primary dispersion step of dispersing in an organic solvent in which 〜40% by weight of a binder is dissolved, and a secondary dispersion step in which an organic solvent in which the remaining binder is dissolved is added to the primary dispersion obtained in the primary dispersion step and dispersed. To have.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly, to a method for producing a pigment dispersion for producing an electrophotographic photoreceptor, and an electrophotographic photoreceptor using the same and having high sensitivity and excellent repetition characteristics. It is about.

[0002]

2. Description of the Related Art In recent years, the use of electrophotography is not limited to the field of copying machines, but has spread to fields in which photographic technology has been conventionally used, such as printing plates, slide films, and microfilms. Also, application to a high-speed printer using a CRT as a light source is being studied. Recently, the use of a photoconductive material other than an electrophotographic photosensitive member, for example, an application to an electrostatic recording element, a sensor material, an EL element, and the like has begun to be studied. Accordingly, demands for photoconductive materials and electrophotographic photoreceptors using the same are becoming higher and wider. Heretofore, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide, and silicon have been known as electrophotographic photoconductors, and have been widely studied and put to practical use. While these inorganic materials have many advantages, they also have various disadvantages. For example, selenium has drawbacks in that the production conditions are difficult and it is easy to crystallize due to heat and mechanical shock, and cadmium sulfide and zinc oxide have poor moisture resistance and durability. It has been pointed out that silicon is insufficient in chargeability and difficult to manufacture. further,
Selenium and cadmium sulfide also have toxicity problems.

On the other hand, organic photoconductive materials have good film-forming properties, excellent flexibility, are lightweight, have good transparency, and are sensitive to a wide wavelength range by an appropriate sensitization method. Due to its advantages such as easy design of the body, its practical use has been gradually attracting attention.

Incidentally, a photoreceptor used in the electrophotographic technique is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charge in a dark place, and (3) charge charge by light irradiation. (4) The residual charge after light irradiation is small.

However, many studies have been made on photoconductive polymers such as polyvinyl carbazole as organic photoconductive substances to date, but these have not always had sufficient film-forming properties, flexibility and adhesiveness. Also, it is difficult to say that the above-mentioned basic properties of the photoreceptor are sufficiently provided.

On the other hand, as for the organic low-molecular-weight photoconductive compound, by selecting a binder or the like used for forming the photoreceptor, the photoreceptor having excellent mechanical strength such as film property, adhesiveness and flexibility can be obtained. Can be obtained, but it is difficult to find a compound suitable for maintaining high-sensitivity properties.

In order to improve such a point, an organic photoreceptor having a higher sensitivity characteristic has been developed in which the charge generation function and the charge transport function are shared by different substances. The feature of such a photoreceptor, which is called a function-separated type, is that a material suitable for each function can be selected from a wide range, and a photoreceptor having an arbitrary performance can be easily manufactured. Has been advanced.

[0008] Of these, the substances responsible for the charge generation function include phthalocyanine pigments, squarium dyes,
Various substances such as azo pigments and perylene pigments have been studied,
Above all, phthalocyanine pigments are expected to exhibit high sensitivity to near-infrared light, and are therefore being put to practical use as photoreceptor materials for laser printers. Phthalocyanine pigments not only have different absorption spectra and photoconductivity depending on the type of central metal, but even with phthalocyanines having the same central metal, there are differences in these properties depending on the crystal form, and a specific crystal form is an electrophotographic photoreceptor. Is reported to be selected.

When an organic material is coated on a conductive support, a solvent-soluble constituent material such as a resin can be applied by dissolving it in a solvent, but is generally insoluble in a solvent such as a pigment. Since such a component cannot be applied as it is, a method of dispersion is necessary. The dispersion described here is to make pigments or the like into fine particles in a solvent to form a suspended state without sediment, and the stability of the dispersion means that the fine particles have a uniform diameter and are stable in the solvent for a long time. It means that it is preserved.

When the dispersibility of pigments and the like is deteriorated, the coated surface becomes rough, which causes an image failure such as pinholes and density unevenness of an electrophotographic photosensitive member. Further, since the dispersed particles settle with the passage of time and the concentration of the dispersion becomes non-uniform, unevenness occurs in the image density between the obtained photoconductors or even on the same photoconductor even when the same coating liquid is applied, For example, the viscosity of the dispersion increases to cause a change in the amount of application, which leads to a decrease in productivity.

In order to obtain a good pigment dispersion, a method of controlling the state of aggregation by changing a part of the molecular structure of the pigment or mixing pigments having different structures, or a method of adding a solvent to the surface of the pigment using a solvent. There is a method of adsorbing a soluble resin. However, these methods use the electrophotographic properties of the original pigment,
That is, the sensitivity, the repetition characteristics, and the like change, and a photoconductor that sufficiently satisfies the basic properties and high durability required for the photoconductor cannot be obtained.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pigment dispersion for producing an electrophotographic photoreceptor having good dispersibility and stability over time and excellent coating properties, and using this dispersion. An object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity and excellent repetition characteristics.

[0013]

Means for Solving the Problems The present inventors have conducted various studies to achieve the above object, and as a result, at least one
In a method for producing a pigment dispersion for electrophotographic photoreceptor production, in which a pigment for a charge generating substance is dispersed in an organic solvent in which at least one kind of binder is dissolved, the pigment dispersion has a solid content concentration higher than the final concentration, And a primary dispersion step of dispersing the entire amount of the pigment for the charge generating substance to be dispersed in an organic solvent in which 1 to 40% by weight of the total binder amount is dissolved in a binder, and the remaining primary dispersion obtained in the primary dispersion step is dispersed in the primary dispersion. The present invention has been found to have a secondary dispersion step of adding and dispersing an organic solvent in which a binder is dissolved, and it is effective to use the pigment dispersion for an electrophotographic photoreceptor.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrophotographic photoreceptor of the present invention can use any of them. For example, there is one in which a photosensitive layer comprising a charge generating substance, a charge transporting substance, and a binder is provided on a conductive support. In addition, a laminated photoconductor in which a charge generation layer composed of a charge generation substance and a binder and a charge transport layer composed of a charge transport substance and a binder are provided on a conductive support is also known. Either of the charge generation layer and the charge transport layer may be an upper layer.

In the construction of the electrophotographic photosensitive member of the present invention, an undercoat layer (blocking layer) for controlling the injection of electric charge from the photosensitive layer to the conductive support is provided between the photosensitive layer and the conductive support. ) May be provided as necessary, and a surface protective layer may be provided on the surface of the photosensitive layer in order to improve the durability of the photosensitive member. In the case of a laminated photoreceptor, an intermediate layer can be provided between the charge generation layer and the charge transport layer.

Hereinafter, each component of the present invention will be described in detail.

As the conductive support according to the present invention, various supports such as those used in known electrophotographic photosensitive members can be used. Specifically, for example, gold, silver, platinum, titanium, aluminum, copper, zinc, iron, conductive metal oxides such as drums, sheets, belts, or laminates of these thin films, deposits and the like Can be

Further, a conductive material such as metal powder, metal oxide, carbon black, carbon fiber, copper iodide, charge transfer complex, inorganic salt, and ionic conductive polymer electrolyte is coated with a suitable binder to form a polymer matrix. Plastics and ceramics embedded inside and subjected to conductive treatment,
Drums, sheets, belts, and the like made of paper and the like, and drums, sheets, belts, and the like of plastics, ceramics, paper, and the like containing such a conductive substance and made conductive.

The undercoat layer is composed of a binder resin alone or a mixture of a binder resin and an inorganic pigment.
Examples of the binder resin include a polyamide resin, an epoxy resin, and a urethane resin. Examples of the inorganic pigment include titanium oxide, zinc oxide, and zirconium oxide.

The thickness of the undercoat layer is determined in accordance with the surface degree of the conductive support and the electrophotographic characteristics at low temperature and low humidity.

The photosensitive layer is formed from a pigment dispersion obtained by dispersing a pigment for a charge generating substance in an organic solvent in which at least a binder is dissolved. The dispersion has a solid content higher than the final concentration, and A primary dispersion step of dispersing the entire amount of the pigment for the charge generating substance to be dissolved in an organic solvent in which 1 to 40% by weight of the total binder amount is dissolved, and adding and dispersing an organic solvent in which the remaining binder is dissolved; It is manufactured by the following dispersion process. The final solid concentration may be set before the secondary dispersion step, or may be adjusted to the final solid concentration during or after the secondary dispersion step. The binder used in the primary dispersion step is 1 to 40% by weight of the total binder amount, preferably 10 to 35% by weight.
And more preferably 15 to 30% by weight. By dispersing the pigment for a charge generating substance by such a method, it is possible to obtain a coating liquid for producing an electrophotographic photoreceptor having good dispersion stability and in which dispersed particles do not settle with time.

The pigment for a charge generating substance used in the present invention includes azo pigments represented by monoazo pigments, polyazo pigments, metal complex salt azo pigments, pyrazolone azo pigments, stilbene pigments and thiazole azo pigments, and perylene anhydride. Pigments, anthraquinone derivatives, anthaniquinone derivatives, dibenzopyrene quinone derivatives, pyranthrone derivatives, biolanthrone derivatives, isoviolanthrone derivatives and the like, and anthraquinone or polycyclic quinones such as perylene imides Pigment, metal phthalocyanine, metal naphthalocyanine,
Examples include phthalocyanine-based pigments typified by metal-free phthalocyanine, metal-free naphthalocyanine, and the like. Among these, when a phthalocyanine pigment is used, 780
In addition to providing an electrophotographic photoreceptor with high sensitivity to long wavelength light around nm and excellent repetition characteristics, the production method of the present invention makes it possible to obtain a pigment dispersion having particularly good dispersibility and stability over time. It is most preferable because it can be obtained.

Among the phthalocyanine-based pigments, a phthalocyanine composition containing titanyloxyphthalocyanine and a metal-free phthalocyanine is particularly preferred because it gives an electrophotographic photosensitive member having excellent sensitivity and repetition characteristics. Among the phthalocyanine compositions, X of CuKα1.541 angstroms
Bragg angle (2θ ± 0.2 °) with respect to line is 27.3 °
A phthalocyanine composition showing a maximum peak is preferable,
The Bragg angles are 7.0 °, 9.0 °, 14.1 °, 1
Phthalocyanine compositions having peaks at 8.0 °, 23.7 ° and 27.3 ° are particularly preferred.

The phthalocyanine composition used in the present invention can be produced by the method described in Japanese Patent Application No. 11-122309 already proposed.

The binder used in the present invention includes:
Acetal resin, butyral resin, vinyl chloride copolymer resin, silicone resin, phenoxy resin, phenol resin, epoxy resin, polycarbonate, polyarylate, polyester, polyamide, polyimide, urethane resin, acrylic resin, etc. are exemplified. Among these,
By using acetal resin and butyral resin,
The pigment dispersion exhibits extremely high dispersibility, and the coatability is also good. Further, by preparing an electrophotographic photoreceptor using the dispersion, the chargeability, sensitivity, and repetition stability are improved. Therefore, in the present invention, it is particularly preferable to use an acetal resin or a butyral resin as the binder. These resins can be used alone or in combination of two or more.

Among the acetal resins, the following general formula (1)
Is preferable, and among butyral resins, a resin represented by the following general formula (2) or (3) is preferable. Among the butyral resins represented by the following general formula (2), those having 60 to 68 mol% of butyral groups and 3 mol% or less of acetyl groups are particularly preferable.

[0027]

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In the formula (1), l, m and n represent integers.

[0029]

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In the formula (2), p, q and r are integers.

[0031]

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In the equation (3), s, t, u, and v are integers.

In the present invention, the solvent used for dispersing the pigment for a charge generating substance includes water or an organic solvent, and may be used alone or as a mixed solvent of two or more kinds. The water may be heavy water or a mixture of water and heavy water. As organic solvents, methanol,
Ethanol, alcohol solvents such as isopropyl alcohol, acetone, methyl ethyl ketone, ketone solvents such as methyl isobutyl ketone, ethyl formate, ethyl acetate,
Ester solvents such as n-butyl acetate, diethyl ether, 1,2-dimethoxyethane, tetrahydrofuran,
Ether solvents such as 1,3-dioxolan, 1,4-dioxane and anisole, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-
Amide solvents such as pyrrolidone, halogenated hydrocarbons such as dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, α-chloronaphthalene, etc. Solvent, carbonization of n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, cumene, etc. Hydrogen solvents can be mentioned. Particularly, among them, ketone solvents, ester solvents and ether solvents are preferable.

In the photosensitive layer, the binder is used in an amount of 10 to 500 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the pigment for a charge generating substance. If the ratio of the resin is too high, the charge generation efficiency is lowered, and if the ratio of the resin is too low, there is a problem in film formability.

In the present invention, an apparatus used for dispersing the pigment for a charge generating substance is a dispersing machine using a dispersing medium such as a ball mill, a paint conditioner, a dyno mill, and an attritor. As the material of the dispersion medium, soda glass, low alkali glass, and zirconia containing yttria are preferable, and beads having a diameter of several mm are often used. According to the production method of the present invention, it is possible to obtain a coating liquid for producing an electrophotographic photoreceptor having good dispersibility and excellent coatability.

In the present invention, when the photosensitive layer contains a charge transport material, the charge transport material used includes a hole transport material and an electron transport material. Examples of the hole transfer material include oxadiazoles disclosed in JP-B-34-5466, triphenylmethanes disclosed in JP-B-45-555, and JP-B-52-4188. Pyrazolines described in gazettes and the like, JP-B-55-423
Hydrazones disclosed in JP-A-80-80, etc .;
Oxadiazoles described in JP-A-123544, etc., triarylamines described in JP-B-58-32372, etc., stilbenes described in JP-A-58-198043, etc. Is mentioned. On the other hand, examples of electron transfer materials include chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,4
7-trinitro-9-fluorenone, 2,4,5,7-
Tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 1,3,7-trinitrodibenzothiophene, 1,3,7-trinitrodibenzothiophene- 5,
5-dioxide and the like. These charge transport materials can be used alone or in combination of two or more.

Among these charge transport materials, hydrazones and stilbenes are preferable because they have high charge (hole) mobility and provide excellent electrophotographic photosensitive members. Among the hydrazones, JP-A-1-100555, JP-A-2-10367, JP-A-2-51163, and JP-A-2-51163
JP-A-96767, JP-A-2-183260, and JP-A-2-183260
JP-A-184856, JP-A-2-184858, JP-A-2-184859, JP-A-2-226160,
The hydrazone compounds described in JP-A-5-188609 and JP-A-7-140686 are particularly preferred. Also, among the stilbenes, JP-A-2-51162, JP-A-2-184857, JP-A-3-75660, JP-A-4-177358, JP-A-6-1948551,
The stilbene compounds described in JP-A Nos. 7-120945, 7-140683, 10-78671, and 10-90923 are particularly preferable.

Further, a certain kind of electron-withdrawing compound can be added as a sensitizer for further increasing the sensitizing effect. Examples of the electron-withdrawing compound include 2,3-
Dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-
Chloroanthraquinone, quinones such as phenanthrenequinone, aldehydes such as 4-nitrobenzaldehyde,
9-benzoylanthracene, indandione, 3,5
-Dinitrobenzophenone, or 3,3 ', 5
Ketones such as 5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride;
Cyano compounds such as terephthalalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, or 4- (p-nitrobenzoyloxy) benzalmalononitrile, 3-benzalphthalide, 3- (α- Phthalides such as cyano-p-nitrobenzal) phthalide and 3- (α-cyano-p-nitrobenzal) -4,5,6,7-tetrachlorophthalide can be mentioned.

In the laminated type photoreceptor, the charge transport layer is constituted by at least a mixture of the charge transport material and the binder. As the binder used for the charge transport layer, polystyrene, an acrylic resin represented by polymethyl methacrylate, polycarbonate having a skeleton represented by bisphenol A or Z, polyarylate, polyester,
Polyphenylene ether, polyether sulfone, polyamide, polyimide, and the like can be used. These binders can be used alone or in combination of two or more.

These binders contained in the charge transport layer are used in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the charge transport material.
00 parts by weight is preferable, and 1 to 500 parts by weight is more preferable. If the ratio of the binder is too high, the sensitivity is lowered, and if the ratio of the binder is too low, the repetition characteristics may be deteriorated or the coating may be damaged.

In the present invention, when the photosensitive layer has a charge transport layer, the charge transport material and the binder contained in the charge transport layer are used after being dissolved in a solvent. Examples of the solvent used include alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl formate, ethyl acetate and n-butyl acetate; and diethyl ether. , 1,2-dimethoxyethane,
Tetrahydrofuran, 1,3-dioxolan, 1,4-
Ether solvents such as dioxane and anisole, N, N-
Amide solvents such as dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromo Benzene, iodobenzene, α
A halogenated hydrocarbon solvent such as chloronaphthalene, n
-Pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane,
Examples include hydrocarbon solvents such as cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, cumene and the like. Among them, ether solvents and halogenated hydrocarbon solvents are particularly preferable.

The electrophotographic photoreceptor of the present invention comprises 2,6-
It is preferable to add an antioxidant such as di-tert-butyl-p-cresol or DL-α-tocopherol to the photosensitive layer. By adding these antioxidants,
An electrophotographic photoreceptor having excellent repetition characteristics can be obtained.

The electrophotographic photoreceptor of the present invention can be coated with a conductive support by a known method such as spin coating, blade coating, knife coating, reverse roll coating, rod bar coating and spray coating. It is obtained by coating and drying on top. In particular, when coating on a drum, a dipping (dip) coating method or the like is used.

[0044]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Alcohol-soluble nylon (manufactured by Toray; CM-8000)
5 parts by weight are dissolved in 100 parts by weight of methanol, 5 parts by weight of titanium oxide (rutile type, manufactured by Sakai Chemical Industry Co., Ltd., R-310) are mixed, and 5 parts by weight of zirconia beads having a diameter of 1 mm are mixed with a paint conditioner manufactured by Red Devil Co., Ltd. Time dispersed. The titanium oxide dispersion thus obtained is applied to a metal aluminum sheet (JIS standard # 1) using an applicator.
050) and dried to form an undercoat layer having a thickness of 0.5 μm.

Butyral resin (manufactured by Sekisui Chemical; BL-2)
25 parts by weight were dissolved in 3000 parts by weight of 1,3-dioxolane, and the solution was added to this solution.
No. 309, and 90 parts by weight of a phthalocyanine composition obtained by the method described in No. 309 and 60 parts by weight of a metal-free phthalocyanine (manufactured by Dainippon Ink and Chemicals, Inc .; 8120), and a paint conditioner manufactured by Red Devil Co., Ltd. For 4 hours together with glass beads having a diameter of 1 mm to obtain a primary dispersion. Next, as a secondary dispersion, a butyral resin (manufactured by Sekisui Chemical; BL-2) is added to the primary dispersion.
A solution obtained by dissolving 75 parts by weight in 9000 parts by weight of 1,3-dioxolane was added, and further dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. The resulting dispersion was applied on the undercoat layer using an applicator and dried to form a charge generation layer having a thickness of about 0.2 μm. Table 1 shows the state of sedimentation of the dispersed particles after the dispersion was allowed to stand for one week.

Next, 100 parts by weight of the stilbene compound represented by (4), polycarbonate (manufactured by Mitsubishi Gas Chemical; Z
-400) 100 parts by weight and 1 part by weight of DL-α-tocopherol (manufactured by Riken Vitamin; E1000) are dissolved in 2000 parts by weight of tetrahydrofuran, and this solution is applied on the charge generating layer with an applicator and dried. ,
A charge transport layer having a dry film thickness of 25 μm was formed.

[0048]

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The electrophotographic photoreceptor thus produced is stored in a dark place at room temperature for 24 hours, then affixed to a drum-shaped aluminum tube and mounted on a commercial office copying machine to form an image.
The image was investigated for any failures. The appearance of the obtained copied image is given in Table 1. Further, using an electrostatic recording tester (Kawaguchi Electric Works; EPA-8200), the photosensitive member was
After being charged at a charging voltage of 5.0 kV, the photosensitive member was irradiated with 2 lux of tungsten light to measure the half-life exposure amount E _1/2 of the photosensitive member. The results are given in Table 2.

Next, the electrophotographic photosensitive member was affixed to a drum tube made of aluminum, and a process speed of 190 mm / sec and a charging voltage of -7. 0 kV, exposure light wavelength 7
Under the conditions of 80 nm and exposure light intensity of ² μW / cm ² ,
Exposure and static elimination were repeated 10,000 times, and before and after that, the charged potential and residual potential of the photoconductor were measured. Table 2 shows the results.

Example 2 35 parts by weight of a butyral resin (BL-2, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 3000 parts by weight of 1,3-dioxolane, and this solution was described in Japanese Patent Application No. 11-122309 already proposed. 150 parts by weight of the phthalocyanine composition obtained according to the method described above were added thereto, and dispersed together with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion. Next, as a secondary dispersion, a solution obtained by dissolving 65 parts by weight of butyral resin (manufactured by Sekisui Chemical; BL-2) in 9000 parts by weight of 1,3-dioxolane is added to the primary dispersion,
Further, the mixture was dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. A photoconductor was prepared using the obtained dispersion in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Tables 1 and 2.

Example 3 10 parts by weight of butyral resin (manufactured by Sekisui Chemical; BL-2) were dissolved in 3000 parts by weight of 1,3-dioxolane, and this solution was described in Japanese Patent Application No. 11-122309 already proposed. 150 parts by weight of the phthalocyanine composition obtained according to the method described above were added, and the mixture was dispersed with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion. Next, as a secondary dispersion, a solution obtained by dissolving 90 parts by weight of butyral resin (manufactured by Sekisui Chemical; BL-2) in 9000 parts by weight of 1,3-dioxolane is added to the primary dispersion,
Further, the mixture was dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. A photoconductor was prepared using the obtained dispersion in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Tables 1 and 2.

Comparative Example 1 50 parts by weight of butyral resin (manufactured by Sekisui Chemical; BL-2) was dissolved in 3000 parts by weight of 1,3-dioxolane, and this solution was described in Japanese Patent Application No. 11-122309 already proposed. 150 parts by weight of the phthalocyanine composition obtained according to the method described above were added thereto, and dispersed together with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion. Next, as a secondary dispersion, a solution obtained by dissolving 50 parts by weight of butyral resin (manufactured by Sekisui Chemical; BL-2) in 9000 parts by weight of 1,3-dioxolane is added to the primary dispersion,
Further, the mixture was dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. A photoconductor was prepared using the obtained dispersion in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Tables 1 and 2.

Comparative Example 2 100 parts by weight of a butyral resin (manufactured by Sekisui Chemical; BL-2) was dissolved in 3000 parts by weight of 1,3-dioxolane, and this solution was described in Japanese Patent Application No. 11-122309, which was already proposed. 150 parts by weight of the phthalocyanine composition obtained according to the method described above were added, and the mixture was dispersed with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion.
Next, as a secondary dispersion, 9000 parts by weight of 1,3-dioxolane was added to the primary dispersion, and the mixture was further dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. A photoconductor was prepared using the obtained dispersion in the same manner as in Example 1, and the same measurement as in Example 1 was performed. Table 1 shows the results
And Table 2.

Comparative Example 3 To 3000 parts by weight of 1,3-dioxolane, 150 parts by weight of a phthalocyanine composition obtained according to the method described in Japanese Patent Application No. 11-122309 already proposed were added. The mixture was dispersed with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion. Next, as secondary dispersion,
Butyral resin (manufactured by Sekisui Chemical; BL-
2) A solution obtained by dissolving 100 parts by weight in 9000 parts by weight of 1,3-dioxolane was added, and further dispersed for 30 minutes by a paint conditioner to prepare a pigment dispersion. A photoconductor was prepared using the obtained dispersion in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Tables 1 and 2.

[0056]

[Table 1]

[0057]

[Table 2]

In Comparative Examples 1 to 3, the dispersion stability of the dispersion prepared from the phthalocyanine composition was poor, and the dispersed particles settled out with the lapse of time, and unevenness and streaks occurred on the coating surface of the charge generation layer. Further, when the electrophotographic photosensitive member was mounted on a copying machine and an image was formed, an image failure such as a pinhole as well as density unevenness was observed. In Comparative Examples 1 to 3, the sensitivity and repetition stability of the electrophotographic photoreceptor were inferior,
The repetition lowers the charging potential and greatly increases the residual potential. If the stability of such repetition is inferior, in the actual copying evaluation, the repetition lowers the contrast of the actually shot image and causes image fogging. On the other hand, in Examples 1 to 3, the dispersion stability of the dispersion liquid prepared from the phthalocyanine composition was good, the sedimentation of the dispersed particles with time was hardly observed, and the applicability was good. Further, the sensitivity of the electrophotographic photoreceptor was high, the repetition characteristics were good, and no image failure was observed when an image was formed by mounting it on a copying machine. Among these, in Example 1 in which the binder used in the primary dispersion step of the pigment dispersion was 15 to 30% by weight of the total binder amount, no sedimentation of the dispersed particles of the dispersion was observed, and Particularly excellent in sensitivity and repetition characteristics.

Example 4 Butyral resin (manufactured by Sekisui Chemical; B
M-2) 25 parts by weight were dissolved in 3000 parts by weight of methyl ethyl ketone, and this solution was added to this solution.
Addition of 150 parts by weight of a phthalocyanine composition produced according to the method described in No. 122309,
The mixture was dispersed with glass beads having a diameter of 1 mm for 4 hours using a paint conditioner manufactured by Red Devil to obtain a primary dispersion. Next, as a secondary dispersion, a solution obtained by dissolving 75 parts by weight of butyral resin (manufactured by Sekisui Chemical; BM-2) in 9000 parts by weight of methyl ethyl ketone is added to the primary dispersion, and further dispersed for 30 minutes by a paint conditioner. Thus, a pigment dispersion was prepared. The obtained dispersion was applied onto the metal aluminum sheet (JIS # 1050) using an applicator and dried to form a charge generation layer having a thickness of about 0.3 μm. The dispersion is
Table 3 gives the state of sedimentation of the dispersed particles after standing for a week.

Next, 100 parts by weight of the hydrazone compound represented by (5), 100 parts by weight of a polycarbonate resin (manufactured by Teijin Chemicals Ltd .; Panlite K-1300), 2,6-di-t
1 part by weight of tert-butyl-p-cresol was dissolved in 2000 parts by weight of tetrahydrofuran, and this solution was applied on the charge generation layer with an applicator and dried.
A charge transport layer having a dry film thickness of 30 μm was formed.

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The electrophotographic photoreceptor thus produced was stored in a dark room at room temperature for 24 hours, and the same measurement as in Example 1 was performed. The results are shown in Tables 3 and 4.

Examples 5 to 9 Butyral resin (manufactured by Sekisui Chemical; BM-2), butyral resin (manufactured by Sekisui Chemical; BM-S), butyral resin (manufactured by Denki Kagaku Kogyo; 6000C), and acetal resin (manufactured by Sekisui Chemical) KS-1), polyester (manufactured by Toyobo;
A photoreceptor was prepared in the same manner as in Example 4, except for changing to Byron 220) and polycarbonate (manufactured by Mitsubishi Gas Chemical; Z-200), and the same measurement as in Example 1 was performed. The results are shown in Tables 3 and 4.

Comparative Examples 4 to 7 In the dispersion of the pigment dispersions of Examples 4 to 7, the photosensitive member was prepared in the same manner as in Example 4 except that the binder was completely dissolved in the primary dispersion step and only the solvent was added in the secondary dispersion step. Was prepared, and the same measurement as in Example 1 was performed. The results are shown in Tables 3 and 4.

[0065]

[Table 3]

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[Table 4]

In Comparative Examples 4 to 7, the dispersion stability of the dispersion prepared from the phthalocyanine composition was poor, and the dispersed particles settled with the passage of time, and unevenness and streaks were generated on the coating surface of the charge generation layer. Further, when the electrophotographic photosensitive member was mounted on a copying machine and an image was formed, an image failure such as a pinhole as well as density unevenness was observed. In Comparative Examples 4 to 7, the sensitivity and the repetition stability of the electrophotographic photoreceptor were poor.
The repetition lowers the charging potential and greatly increases the residual potential. If the stability of such repetition is inferior, in the actual copying evaluation, the repetition lowers the contrast of the actually shot image and causes image fogging. On the other hand, in Examples 4 to 9, the dispersions prepared from the phthalocyanine compositions had good dispersion stability, little sedimentation of the dispersed particles over time, and good coatability. Further, the sensitivity of the electrophotographic photoreceptor was high, the repetition characteristics were good, and no image failure was observed when an image was formed by mounting it on a copying machine. Among them, Example 4 using butyral resin as a binder of a pigment dispersion liquid
Nos. 6 to 6 and Example 7 using an acetal resin, no sedimentation of the dispersed particles of the dispersion was observed, and the sensitivity and repetition characteristics of the electrophotographic photosensitive member were particularly excellent.

Example 10 20 parts by weight of a butyral resin (manufactured by Denki Kagaku Kogyo; 5000A) was dissolved in 3000 parts by weight of 1,2-dimethoxyethane, and this solution was added to this solution.
No. 09, 150 parts by weight of the phthalocyanine composition obtained by the method described in No. 09, and a diameter of 1 mm with a paint conditioner manufactured by Red Devil Co., Ltd.
The mixture was dispersed for 4 hours with glass beads having a diameter of 1 mm to obtain a primary dispersion. Next, as a secondary dispersion, a solution obtained by dissolving 80 parts by weight of butyral resin (manufactured by Denki Kagaku Kogyo; 5000A) in 9000 parts by weight of 1,2-dimethoxyethane is added to the primary dispersion, and a paint conditioner device is further added. For 30 minutes to prepare a pigment dispersion. The obtained dispersion was applied on an aluminum vapor-deposited polyester using an applicator and dried to form a charge generation layer having a thickness of about 0.2 μm. Table 5 shows the state of sedimentation of the dispersed particles after the dispersion was allowed to stand for one week.

Next, 100 parts by weight of the stilbene compound represented by (4), 100 parts by weight of a polycarbonate resin (manufactured by Teijin Chemicals Ltd .; Panlite K-1300), 2,6-di-t
1 part by weight of tert-butyl-p-cresol was dissolved in 2000 parts by weight of tetrahydrofuran, and this solution was applied on the charge generation layer with an applicator and dried.
A charge transport layer having a dry film thickness of 20 μm was formed.

The electrophotographic photosensitive member thus produced was stored in a dark room at room temperature for 24 hours, and the same measurement as in Example 1 was performed. The results are shown in Tables 5 and 6.

Examples 11 to 14 Each of the phthalocyanine compositions was titanyloxyphthalocyanine (manufactured by Sanyo Dye; T-22S), metal-free phthalocyanine (manufactured by Toyo Ink; TPA-891), and bisazo pigments represented by the following formula (6): Example 1 was changed to a perylene pigment (manufactured by Dainichi Seika Kogyo; DPA-1).
A photoconductor was prepared in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Tables 5 and 6.

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[Table 5]

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[Table 6]

In Examples 10 to 14, the dispersion stability of the pigment dispersion was good, the sedimentation of the dispersed particles with time was hardly observed, and the coatability was good. Furthermore, the sensitivity of the electrophotographic photosensitive member is high, the repetition characteristics are good, and even if an image is formed by mounting it on a copying machine, there is no problem at all, as small black spots are slightly observed. Among these, in Examples 10 to 12 using a phthalocyanine pigment as the charge generating material pigment, sedimentation of dispersed particles of the dispersion was not observed at all, and the sensitivity and repetition characteristics of the electrophotographic photoreceptor were particularly excellent. It is particularly preferable because no minute black spots are observed even when an image is formed by mounting the apparatus on a copying machine. Among them, Example 10 using a phthalocyanine composition containing titanyloxyphthalocyanine and metal-free phthalocyanine shows the best characteristics.

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As is apparent from the above, according to the present invention, a pigment dispersion for producing an electrophotographic photoreceptor having good dispersibility and stability over time and excellent coating properties is produced. Can be used to provide an electrophotographic photosensitive member having high sensitivity and excellent repetition characteristics.

Claims (9)

[Claims] 1. A method for producing a pigment dispersion for producing an electrophotographic photoreceptor, comprising dispersing a pigment for a charge generating substance in an organic solvent in which at least one or more binders are dissolved,
A primary dispersion step of dispersing the pigment dispersion at a solid concentration higher than the final concentration, and dispersing the entire amount of the pigment for a charge generating substance to be dispersed in an organic solvent in which 1 to 40% by weight of the total binder is dissolved in an organic solvent; And a secondary dispersion step of adding an organic solvent in which the remaining binder is dissolved to the primary dispersion liquid obtained in the primary dispersion step, and dispersing the resultant dispersion. 2. The method according to claim 1, wherein the amount of the binder used in the primary dispersion step is 15 to 30% by weight based on the total amount of the binder. 3. The method for producing a pigment dispersion for producing an electrophotographic photosensitive member according to claim 1, wherein an acetal resin is used as the binder. 4. The method for producing a pigment dispersion for producing an electrophotographic photosensitive member according to claim 1, wherein a butyral resin is used as the binder. 5. The method for producing a pigment dispersion for producing an electrophotographic photosensitive member according to claim 1, wherein the pigment for a charge generating substance is a phthalocyanine pigment. 6. The phthalocyanine composition according to claim 1, wherein the pigment for a charge generating substance is a phthalocyanine composition containing titanyloxyphthalocyanine and a metal-free phthalocyanine.
5. The method for producing a pigment dispersion for producing an electrophotographic photoreceptor according to any one of items 4. 7. A phthalocyanine composition containing a titanyloxyphthalocyanine and a metal-free phthalocyanine, wherein the pigment for a charge generating substance is CuKα.
Bragg angle (2θ) for X-rays of 1.541 angstroms
The method for producing a pigment dispersion for producing an electrophotographic photosensitive member according to any one of claims 1 to 4, wherein (± 0.2 °) has a peak at 27.3 °. 8. The pigment for a charge generating substance is a phthalocyanine composition containing titanyloxyphthalocyanine and a metal-free phthalocyanine, and the composition is CuKα.
Bragg angle (2θ) for X-rays of 1.541 angstroms
± 0.2 °) is 7.0 °, 9.0 °, 14.1 °, 1
The method for producing a pigment dispersion for producing an electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the pigment dispersion has peaks at 8.0 °, 23.7 °, and 27.3 °. 9. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer is at least one of claims 1 to 8.
An electrophotographic photosensitive member formed using the pigment dispersion for producing an electrophotographic photosensitive member according to any one of the above.